private void HinhThucChoVay_Click(object sender, EventArgs e) { if (HinhThucVayfrm == null || HinhThucVayfrm.IsDisposed) { HinhThucVayfrm = new frmHinhThucVay(); HinhThucVayfrm.MdiParent = this; HinhThucVayfrm.Show(); } else { HinhThucVayfrm.Activate(); } }